Re: [PATCH] cgroup: don't queue css_release_work if one already pending

[Tadeusz Struk]

On 5/20/22 09:42, Michal Koutný wrote:
> On Fri, May 20, 2022 at 09:38:12AM -0700, Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> wrote:
> > as this is a result of enqueuing the same css->destroy_work onto the same WQ,
> > one on the rcu path and one on the css_release path.
> > I will prototype it today and test with syzbot.
>
> In my understanding, you'd need two independent work_structs in a css,
> not two separate workqueues to put the single entry on.

Yes, separating the css_killed_ref and css_release paths with two separate work_structs
fixes the two syzbot list corruption issues [1]&[2].
I tested it on mainline v5.18.0 and v5.10.117
In case of [2] the mainline triggers an issue, but it is unrelated to list corruption.

[1] https://syzkaller.appspot.com/bug?id=e26e54d6eac9d9fb50b221ec3e4627b327465dbd
[2] https://syzkaller.appspot.com/bug?id=3c7ff113ccb695e839b859da3fc481c36eb1cfd5

I will send a patch soon.

--
Thanks,
Tadeusz